| CPC H04B 10/615 (2013.01) [H04B 10/6163 (2013.01)] | 20 Claims |
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1. A device, comprising:
a coherent optical receiver system configured to receive optical signals; and
a filter system configured to equalize the optical signals,
wherein the filter system includes a first filter that provides a first filtering characteristic, a second filter that provides a second filtering characteristic, and a third filter that provides a third filtering characteristic,
wherein an adjustment rate of the first filter and an adjustment rate of the second filter are each at least ten times an adjustment rate of the third filter, and
wherein at least one of:
a frequency finesse of the first filter is at least four times finer than a frequency finesse of the second filter,
a contiguous frequency range of the first filter is less than a first predefined number of Fast Fourier Transform (FFT) bins,
the frequency finesse of the first filter is per FFT bin,
the frequency finesse of the third filter is per FFT bin,
the frequency finesse of the second filter is greater than a second predefined number of FFT bins,
the first filter is functionally in parallel with the second filter,
the optical signals comprise a plurality of frequency division multiplexed (FDM) streams and a roll-off factor of each FDM stream of the plurality of FDM streams or at least one FDM stream of the plurality of FDM streams is less than a third predefined value,
the optical signals comprise a plurality of FDM streams and a frequency separation between centers of neighboring FDM streams of baud rates B1 and B2 is less than a constant multiplied by (B1+B2) in Hertz,
the optical signals comprise a plurality of FDM streams and a frequency gap between neighboring FDM streams is less than a peak-to-peak laser frequency deviation, or
an estimate of an intermediate frequency (IF) is used to control the first filter and the control of the first filter comprises an interpolation.
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